(a) A gas utility may put a changed rate into effect by filing a bond with the regulatory authority if the regulatory authority fails to make a final determination within 90 days from the date the proposed increase would otherwise be effective.
(b) The bonded rate may not exceed the proposed rate.
(c) The bond must be:
(1) payable to the regulatory authority in an amount, in a form, and with a surety approved by the regulatory authority; and
(2) conditioned on refund.
(d) The gas utility shall refund or credit against future bills:
(1) money collected under the bonded rates in excess of the rate finally ordered; and
(2) interest on that money, at the current interest rate as determined by the regulatory authority.